Gravity sei aration of ores



y v 1940- H. H. WADE GRAVITY SEPARATION OF QRES Filed March 31, '1938 2 Sheets-Sheet l Hash/Wafer H Inventor llllllll Cr ude Ora 5/ Fefu/"n r70 an asfe Con veyor JWhz A Z rnezis July 9, 1940. H WADE 2,206,980

GRAVITY SEPARATION OF ORES Invenior Patented July 9, 1940 UNITED STATES PATENT OFFICE I mesne assignments, to Minerals Beneficiation, Incorporated, acorporation of Delaware Application March 31,

16 Claims.

This invention relates to the gravity separation of the heavier ores from their impurities or tailings in a fluid mass consisting of liquid, preferably water, and solids insoluble in the liquid and of such character and fineness that by slight agitation of the mixture a uniform mass having a specific gravity within the range of 2.5 to 3.3 may be maintained.

Heretofore, the solid, insoluble constituents of m the flotation mediums used in methods for concentrating ores,. such as iron, manganiferous iron, copper, lead and zinc ores, by gravity, have not been satisfactory because of the difficulty of separating the mediums from the ore concen- 15 trate and the resulting contamination of the concentrates by the introduction of objectionable impurities such as lead and sulphur or compounds of either or both of these objectionable constituents of the medium. The crude ores re- 20 ferred to have such a high specific gravity that in order to float the rock, sand and other tailings in a body of fluid medium the medium must have a specific gravity in some cases in excess of 2.5 and in order to obtain a fluid mass of the 25 required density and at the same time provide the necessary fluidity it is essential that the solid constituent of the medium have a specific gravity in excess of 6.

By the present invention crude ores having a 30 specific gravity in excess of 2.5 may be concentrated in a novel fluid mass containing comminuted solids of magnetic susceptibility which solids are then separated from the ore concentrates and tailings by magnetic attraction.

The invention further provides a continuous novel process for maintaining a predetermined specific gravity in such a flotation medium and repeatedly utilizing substantially all of the solid constituents of the medium while separating the 40 medium from both the tailings and concentrates and delivering the latter substantially free of the medium.

As the preferred solid constituent of the medium, I employ ferro-silicon, reduced to minus 65 to 100 mesh, and containing in excess of 75% by weight of iron. For the concentration of certain iron ores, a ferro-silicon containing about 82% iron, 13% to 14% silicon and a small amount of carbon has been used successfully. Such ferro- 50 silicon is preferably ground to minus 100 mesh and a medium is formed therefrom by mixing the fine ferro-silicon with about 25% of its weight of water. Such ferro-silicon is highly rust resistant, is recoverable from the tailings and concen- 55 trates by magnetic attraction and has the jur- 1938, Serial No. 199,197 209-39) ther advantage of being so hard that it may be used repeatedly without deterioration. It has a hardness of about 7, Mohs scale, and its specific gravity is about 7.5. As a substitute for the ferro-silicon, high carbon steel may be used having an iron constituent in excess of 75% by weight. High carbon steel in finely divided form makes a good medium but normally is not so rust resistant as ferro-silicon and hence is subject to higher losses due to oxidation in the liquid medium.

My preferred procedure for utilizing suchmetaLlic mediums in the concentration ofores will be best understood by reference to the accompanying drawings in which:

Figure 1 is a diagrammatic illustration of suitable apparatus and connections for carrying out the process;

Fig. 2 is a somewhat enlarged, central vertical section through the preferred form of concentration tank;

Fig. 3 is a plan view of the lower part of the concentrating chamber, and

Fig. 4 is a plan view of the head box for distributing the medium to the tank.

Referring to Fig. 1, the numeral 5 indicates a bin or hopper for the crude ore which in the case of iron ore is preferably reduced to about one inch mesh and is continuously fed from the hopper to a conveyor 6, deliver a stream of ceptacle 1. From the ore into a funnel-like rethis receptacle the ore passes by gravity through a pipe 8 into the upper part of a concentrating tank indicated generally by the numeral 9. The lower portion 1 0 of this tank has the form of an inverted cone and has a central opening in its bottom to deliver the settled ore concentrate into a pipe II. The upper portion I! of tank 9 is also conical but converges upwardly to a restricted top opening, its upper periphery l3 extending horizontally to deliver the floated tailings and a portion of the fluid medium into an annular launder It. This launder delivers the overflow to the upper end of an inclined screen l5, preferably of the punch plate type having a multiplicity of openings about two millimeters in diameter. The tailings are retained on the screen while the bulk of the liquid and solid constituents of the medium pass through it into a catch basin l6 mounted beneath the screen near its upper end. The tailings with adhering particles of medium and of fine tailings, continue down the screen l5. Suitable means for jigging the screen l5 may be provided to augment the gravitational movement of the tailings 55 operating continuously, to 30v the medium or tailings.

down along this screen, in accordance with the common practice in this art. While in 'motion down the lower portion of the screen, the tailings are subjected to water sprays issuing from pipes I1. This spray washes of! the adherins particles of medium and fine tailings into a catch basin. I3 and the washed tailings are discharged from the lower end of the screen I.

A liquid flotation medium, ing of 80% by weight silicon and about 20% by weight of water is delivered into a head box I! and thence passes through a series of supply pipes 20 communicating with the tank 9 at a number of points uniformly distributed around the periphery of the tank and at a substantial distance below the upper periphery l3 thereof. This medium, which has a specific gravity of about 3, fills the tank 9 and is continuously supplied in sufilcient volume and at such velocity as to maintain the solid constituent thereof in suspension. .A portion of the medium overflows the periphery l3 of the tank 9 and carries with it the tailings consisting largely of rock and sand.- Medium also flows down through the lower portion III of the concentrating tank'and out through the pipe II with the ore concentrates which have settled out due to their higher specific gravity than either The greater part oi the overflow fluid medium passes through the screen l5 into the basin Hi from which it is delivered into a'pipe 2| arranged to supply an air lift 22. Air under pressure is injected into the lift 22 through a pipe 23 and carries the liquid medium up through a pipe 24 which returns the medium to the head box I9.

The concentrates and some medium are discharged from the bottom of the tank 9 through the pipe H and are carried by an air lift 25 and pipe 26 to the upper end of a screen 21. This screen is like the screen' l5 and carries the ore concentrate in a thin layer or stream to the lower end of the screen from which the ore falls into a suitable receptacle or pile. The bulk of the medium, after flowing from the pipe 25, passes through the screen into a basin 28 and thence through a pipe 29, air lift 30 andpipe 3| back into the head box l9. As the ore concentrate passes down the screen 21, it is subjected to a water spray from pipes 32, which spray removes the adhering particles of medium and fines from the concentrates and washes them into a basin 33 extending beneath the screen.

The wash water, carry g the tailing fines, some form silicon and concentrate fines, is discharged from the basins l8 and 33 into pipes 34 .and 35 respectively extending to a suitable pump 36. This pump discharges the fluid mixture through a pipe 31 into a receptacle 38 which distributes the liquid and fines in a thin stream over a plate 39. Moving adjacent to the plate 39 is a belt 40 having electro-magnets 4| above it. These magnets are supplied with direct current and the belt is continuously driven in the direction indicated by arrows. The belt 40 moving in the field of the magnets 4i, passes closely adjacent to the stream fiowing over the plate 39 and picks up, by magnetic attraction, on its bottom surface substantially all of the ferrosilicon while the particles of tailings, being nonmagnetic, are not lifted by magnetic attraction, but fall from the end of the plate 39, together with the greater part of the water constituent, into waste hoppers 42. From these hoppers the non-magnetic particles and water are discharged preferably consistof finely divided ferrothrough pipes 43. The belt 40 carries the adhering particles of ferro-silicon to a point somewhat beyond the infiuence of the electro-magnets 4| at which point such particlesare released from the belt and fall into a hopper 44, in which the water is largely free from waste products. From this hopper the medium passes'through a-pipe into a settling tank 45 containing water in a sufficiently quiescent state to perm't the metallic solids to settle to the bottom. As these solids remain in their polarized condition, the smaller particles adhere to the larger ones and the settlingis accelerated due to the resulting adherence of the particles to each other, until the subsequent demagnetizing treatment. The solids are thus concentrated in the water in tank 46 to secure a medium of the required specific gravity and the medium is then removed from the bottom of the tank 45 by an outletpipe 41. During removal of the medium from the tank 46, rake arms 48 are slowly rotated by power applied to a supporting shaft 49. The pipe 41 carries the concentrated medium, having a specific gravity in excess of 2.5 axially through a de-magnetizer 50, which'is supplied with aternating current. The residual magnetism of the particles is thus destroyed so that they maybe readily diffused in the fluid mass, The pipe 41 then returns the demagnetized concentrated medium to the head box l3.

Water is displaced from the top of the tank 46 and may be collected in a launder 5| together with such small amounts of the magnetic solids as are carried over by the water. This launder discharges through a pipe 52 into a magnetic log washer 53 which separates the magnetic solids from the bulk of the water. The magnetic solids are discharged from this washer through a demagnetizer 54 and are returned to the head box I9 through a pipe 55 and the pipe 24. The use of the magnetic log washer 53 is optional and 'in some cases it may be practical to merely waste the overflow from the settling tank 46.

As shown in Figs; 2 and 4, the lower portion of the head box I9 is divided by partitions 56 into separate outlet chambers. The upper edges of the partitions 56 extend in a common horizontal plane and the several pipes 20 communicate respectively with several outlet chambers thus formed. The upper'surface of the medium in the box I9 is maintained above the upper edges of the partitions 56 so that the several pipes 20 are uniformly supplied with medium.

To prevent the building up of the ore concentrate on the conical walls of the lower portion In of the tank 9, rake arms 51 are arranged to extend parallel to elements of the conical surface and -are slowly rotated within the tank. The upper ends of the several arms 51 are rigidly secured to a ring 58 and this ring'has arms 59 connecting it to a central shaft 60 which'projcts from the top of the tank 9 and is arranged tobe rotated by suitable mechanism, such as-the gearing indicated at 6| (Fig. 2).

It is not essential that the crude ore be crushed to about one inch size, as hereinbefore described, and crushing to much larger or smaller sizes is frequently desirable although the equipment must be designed to handle the particular size selected. In the recovery of the solid from the wash water, it is sometimes desirable to pass the fluid from the pipe 31 through a thickener or dewaterin equipment of suitable design before conducting the solids to the receptacle 38. Thickening or dewatering treatment of the overflow from the v the magnetic log washer 53.

It will now be evident that the process herein described is a continuous one in which the' ore concentrates, substantially free from the flotation medium, are discharged from the screen 21 while the tailings, washed free of the medium, are discharged from the screen l5.v The solid constituents, of the flotation medium are recovered magnetically and continuously, substantially free of impurities and returned,- after being demagnetized, to the gravity separation tank.

The ferro-silicon of the medium, in addition 'to having a high specific gravity, is highly resistant to rust and is very hard and can be obtained at low cost. 'I'l'iese'characteristics make it unusually practical for use in concentrating ores of high specific gravity. Further, because of its magnetic character substantially all of it may be recovered so that it has a long, useful life in the process and may be circulated many times through the concentration tank. As a result of these features, the specific gravity of the medium in the concentration tank may be controlled accurately at the predetermined high point required for the concentration of the particular ore to be treated.

The ores which may be concentrated by my improved-method require fluid mediums having specific gravities within the limits of about 2.5 to 3.3 and for each ore the gravity of the medium must'be controlled within a narrow range. Ferro-silicons for use in forming the medium are available having specific gravities varying from about 6.5 to'7.5, depending on the porosity as well as the chemical composition.

The expression iron composition, as used in the appended claims, is intended to include ordinary and. eutectic mixtures, alloys and compounds of iron and steel where the iron constituent exceeds 75%, by weight, of the composition.

Having described my invention, what I claim as new and desire to protect by Letters Patent is:'

1. The method of concentrating an ore which consists in delivering the crudeore into a fluid mass consisting of an iron composition and water, said. composition containing in excess "of 75% by weight of magnetic iron, maintaining the speciflc gravity of said mass at such point as to float the tailings from the ore and to allow the ore concentrate to settle therein, separately removing the ore concentrate and tailings from the mass, washing said tailings and ore concentrate to remove adhering particles of said mass theresisting of an iron composition and a liquid, said composition containing in excess 01' 75% by weight ,of iron, continuously floating the lighter f 5'.

constituents of the ore in said mass and allowing the heavier constituents to settle therein, separately removing the heavier and lighter constituents of the ore from said. mass, washing the iron composition irom the separated ore constituents, recovering said-composition from the wash water by magnetic attraction, de-mag'netiz ing the recovered iron composition and returning the de-magnetized composition so recovered to said mass.

3. The method of concentrating an ore which consists in introducing the ore into a fluid mass consisting of ierro-silicon and a liquid, said ierro-silicon containing in excess of 75% by weight of iron, continuously floating the tailings from the ore in said mass and allowing the ore concentrate to settle in said mass, removing the ore concentrates and a portion of said mass from the lower part of said mass, withdrawing the tailings and a portion of said mass from the -upper part or said mass, washing the ierro-silicon from the separated ore and tailings,'recovering the ierro-silicon irom the wash water by magnetic attraction and returning the ferro-silicon so recovered to said mass.

4. The method of concentrating iron ore and manganiferous iron ore having a specific gravity in excess of 2.5 which consists in delivering the crude ore into a fluid mass consisting of terrosilicon and water, the ferro-silicon containing approximately 82% by weight of iron and in,

settle therein, continuously removing the ore concentrate and a portion of said medium from the lower part of said mass, continuously withdrawing the tailings and a portion of said medium from the upper part of said mass, continuously separating the bulk of the withdrawn medium from the tailings and ore concentrate, returning the separated medium to said fluid mass, washing the term-silicon from the separated ore and tailings, recovering the ierro-silicon from the wash water by magnetic attraction and returning the ferro-silicon so recovered to said mass.

6. The method of concentrating an ore which consists in continuously introducing the ore into a fluid mass oi flotation medium consisting of finely divided iron'composition and a liquid, continuously floating the lighter constituents from the ore in said medium and allowing the heavier constituents to settle therein, continuously 'withdrawing the heavier crude ore constituents and a portion of said medium from the lower part of said mass, continuously withdrawing the lighter crude ore constituents and a portion of said medium from the upper part of said mass, continuously separating the bulk of the withdrawn medium from the ore constituents so withdrawn, returning the separated medium to said fluid mass, washing the iron composition of the medium from the separated ore constituents, recovering the iron composition of the medium from the wash water'by magnetic attraction and returning the iron composition so recovered to said mass.

'7. The method of concentrating an ore which conslsts in delivering the crude oreinto a fluid mass consisting 01 an iron composition and water, said composition containing in excess of 75% by weight of magnetic iron, maintaining the speciflc gravity of said mass at such point as to float the tailings from the ore and to allow the ore,

concentrate to settle therein", separately. removing the ore.concentrate andtailingsirom the move adhering particles of said fluid mass therefrom, magnetizing the particles of iron composition in the wash water and recovering said particles from the wash water by magnetic attraction, then concentrating said particles by utilizing their residual magnetism to V accelerate their settling in a liquid, then de-magnetizing said particles and returning them to the fluid mass.

8. The method of concentrating an ore having a specific gravity greater than 2.5, which consists in delivering the ore to a fluid mass in which the heavier particles sink and the lighter particles float and consisting of approximately 20% by weight of water and a rust resistant iron composition in which composition the iron constituent exceeds by weight, and maintaining the specific gravity of the fluid mass intermediate the specific gravities of the ore particles to be separated.

9. The process which consists in introducing a finely comminuted non-abrasive, rust resistant solid having magnetic susceptibility into a liquid to secure a liquid medium having a desired specific gravity, introducing said medium mass into a container introducing the one into said medium, floating ore particles having less specific gravity than that of the medium to the surface of said medium, removing said lighter particles and some medium from the container, and recovering said comminuted solids from the removed medium by magnetic attraction.

10. In a continuous process for separating ore constituents employing a liquid separating medium, the steps of subjecting the ore to a body of liquid separating medium containing a finely divided rust-resistant metal or magnetic susceptibility and wherein some of the ore particles fioat and some sink, removing the separated particles and some medium from the main-body of medium, and recovering the metal from the removed medium by magnetic attraction. I

11. A process of concentrating ores which consists in introducing a finely comminuted rust resistant iron alloy having magnetic susceptibility into a liquid to secure a liquid medium having a desired specific gravity, introducing said medium into a container, introducing the ore into said medium, floating ore particles having less specific gravity than that of the medium to the surface of the medium, removing said lighter particles and some medium from the container and recovering said alloy from the removed medium by magnetic attraction.

ering said comminuted ferro silicon from the re' moved medium by magnetic attraction. 13. In -a process for concentrating ore, the

steps'of introducing the ore into a gravity liquid flotation medium consisting of magnetically attractive rust resistant ferro silicon and water, the term silicon and water mixed in proportions to form a liquid gravity separating medium having a specific gravity intermediate the specific gravities of the ore particles to be separated, separating the ore constituents in said medium, re-

moving the separated constituents together with some of the medium, and then recovering the term silicon from said separated medium by magnetic attraction.

14. The method of concentrating ores which consists in introducing the ore into a fluid mass of flotation medium consisting of finely divided ierro-silicon and water, continuously removing tailings and concentrates and a portion of said medium from said fluid mass, separating the bulk of the removed medium from the removed tailings and concentrates, returning the separated medium to said fluid mass, washing the ferro silicon from the separated tailings and concentrates and recovering the term silicon from the wash water by magnetic attraction.

15. In a process of separating ores, the step of introducing the ore into a liquid medium consisting of water and a comminuted magnetically attractable ru st resistant iron alloy mixed in proportions to form a liquid gravity separating medium having a specific gravity intermediate the specific gravities of the ore particles to be separated.

16. In a process of separating ores, the step of introducing the ore into a liquid medium consisting of water and a comminuted magnetically attractable oxidation resistant metallic alloy mixed in proportions to form a liquid gravity separating medium having a specific gravity intermediate the specific gravities of the ore particles to be separated.

HENRY H. WADE.

' CERTIFICATE CF CORRECTION. Patent No. 2,206,980. July 9, 191m.

HENRY H. WADE.

It is hereby certified that error appears in the printed specification of the above mmbered patent requiring correction as follows: Page 1 first column, line 26, claim 9, for the words "container introducing the one" read. -container, introducing the ore--; and that the said Letters Patent d oulzi be read with this correction therein that the sane may conform to the record of the case in the Patent Office.

Signed, and sealed this 15th day of August, A. D. 191 0.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents. 

